A process of manufacturing a semiconductor device includes a back-grinding or dicing process, and uses a pressure-sensitive adhesive sheet such as a wafer surface protective sheet or a dicing sheet.
Recently, according to the increasing demands for smaller and lighter semiconductor devices, performance of such a pressure-sensitive adhesive sheet for processing a wafer becomes more important.
For example, to achieve a higher integration rate than a conventional method of forming a circuit only on one surface of a wafer, recently, there is an attempt to forming a circuit on both surfaces of the wafer. Likewise, to form circuits on both surfaces of the wafer, a high temperature process should be performed in a state in which a sheet for processing a wafer is attached. Accordingly, the sheet for processing a wafer needs excellent thermal resistance or dimensional stability at a high temperature. However, when a solid substrate having a high melting point is used to simply ensure the thermal resistance or dimensional stability, a function of protecting a wafer and stress relaxation are degraded, and thus the wafer may be damaged.
In addition, the substrate of the sheet for processing a wafer has excellent stress relaxation and no defect such as a fish eye. That is, when the stress relaxation is degraded or a protrusion is creased on the substrate, the wafer is probably damaged due to remaining stress or the application of a non-uniform pressure in the process. Such demands are higher according to the increase in demand for a large diameter wafer.
Moreover, the sheet for processing a wafer also needs excellent cuttability. When the cuttability is decreased, a cutting failure may be generated during the processing of the wafer, and in this case, the process of processing a wafer is discontinuously performed. Accordingly, when the cuttability of the sheet for processing a wafer is degraded, process efficiency may be degraded and the wafer may be damaged.